Expanding ligament graft fixation system and method

ABSTRACT

A graft fixation system for fixing graft material in a bone tunnel includes an expandable fixation member having a graft receiving eyelet disposed proximate its distal end, opposed bone engaging elements disposed about its periphery, and an expansion plug receiving opening defined in its proximal end. The system also includes an expansion plug having a diameter greater than the diameter of the expansion plug receiving opening so that forceable insertion of the expansion plug into the expansion plug receiving opening causes an expansion of the expandable fixation member driving the opposed bone engaging elements apart so as to fix the bone engaging elements, as well as the graft material, in a bone tunnel.

FIELD OF THE INVENTION

The present invention relates to systems and methods for locking andintegrating soft tissue with bone. More specifically, systems andmethods for use in conjunction with ligament replacement surgery aredescribed.

BACKGROUND OF THE INVENTION

The complete or partial detachment of ligaments, tendons or other softtissues (hereinafter “ligamentary material”) from the bones with whichthey are associated are commonplace, particularly among athletes. Suchinjuries usually result from excessive stress being applied on thesetissues. Some degree of tissue detachment may occur, for instance, asthe result of an accident, overexertion during a work-related activity,stress during the course of an athletic event, or in conjunction withnumerous other situations and activities. If, however, ligamentarymaterial is completely detached from its associated bone(s) or issevered, partial or permanent disability may result.

Fortunately, there are numerous surgical techniques known and used inthe art for reattaching detached tissues and/or completely replacingligamentary material. One such technique involves the use of“traditional” fasteners (e.g. metal staples, cancellous bone screws.)Such fasteners have also been used to attach tendon or ligamentsubstitutes (often formed of autogenous tissue harvested from elsewherein the body, collectively referred to herein as “grafts” or “graftmaterial”) to the desired bone(s). A common surgery involves replacingor repairing the anterior cruciate ligament (ACL) in a human knee. Bonetunnels are appropriately aligned and formed in both the proximal tibiaand the distal femur during the course of this surgery. Graft materialis somehow rigidly coupled, usually with bone blocks to be inserted intothese tunnels, to fix the material in a proper position for long termuse in the body.

Such ligament fixation schemes have not been entirely successful. Forexample, rigid attachment using “traditional” attachment devices such asstaples, sutures and screws often cannot be maintained even under normaltensile loads. Also, the use of sharp screws to create a lockinginterference fit between a bone plug/block and a bone tunnel may beproblematic. For instance, there is always the possibility of damagingthe ligament during insertion of the screw. In addition, it may bedifficult to maintain the desired tension on the graft material duringinsertion of the screw. Alternative, non-rigid fixation schemes (such assuspending a ligament graft from a suture button) also have drawbacks.Because the graft structure is not, in such schemes, rigidly fixedwithin the bone tunnels, movement of the graft structure may disrupt thehealing process. It is known that intimate contact between the graftmaterial and the walls of the bone tunnels aids in ensuring aneffective, efficient healing process.

Another potential problem may arise even where the graft materialappears to be successfully fixed within the bone tunnel. Bone tunnelsare usually drilled for a considerable length into the femur forfixation of the graft material in ACL replacement procedures. Whereexactly within the tunnel the graft is fixed often depends on the mannerof fixation and tensioning of the graft material, but often the site forfixation is chosen as the place where the fixation device best allowsfixing. Where the fixation takes place inside the bone tunnel apart fromthe bone tunnel edge at the distal end of the femur, the graft materialthat extends from the fixation point to the edge of the bone tunneloften moves or slides within this remaining portion of the tunnel. Thisphenomenon is known to some surgeons as the “windshield wiper” effect.As noted above, movement tends to prevent healing and fixation of thesoft tissue to bone, so where the windshield wiper effect occurs, theportion of the graft that moves when the patient uses the reconstructedjoint may never heal completely in the region near the edge of the bonetunnel. This potential problem defeats the goal of most surgeons whichis to have the graft material fix as close as possible to its naturalfixation point before being damaged by injury or disease. This naturalfixation point is generally at the edge of the bone tunnel, where thegraft will not fix if the windshield wiper effect is present.

Accordingly, there is a need for ligament graft fixation devices thatreliably provide fixation of graft material in the region closest to thenatural fixation point of the ligamentary material being replaced.

SUMMARY OF THE INVENTION

The present invention provides a ligament graft fixation system forfixing ligament graft material within a bone tunnel in a way that betterapproximates the natural fixation point of the ligamentary material thatis being replaced. The system of the invention includes an expandablefixation member having a graft receiving eyelet disposed proximate itsdistal end, opposed bone engaging elements disposed about its periphery,and an expansion plug receiving opening defined in its proximal end. Thesystem also includes an expansion plug having a diameter greater thanthe diameter of the expansion plug receiving opening so that forceableinsertion of the expansion plug into the expansion plug receivingopening causes an expansion of the expandable fixation member to drivethe opposed bone engaging elements apart so as to fix the bone engagingelements, as well as the graft material, in a bone tunnel. The fixationsystem of the invention allows for fixation at the proximal end of thefixation member, which can be placed proximate to the edge of the bonetunnel to fix the graft as close to the anatomically correct position asdesired.

Specific embodiments of the fixation system of the invention includethose having graft receiving grooves extending distally from the eyelet,including embodiments where the grooves are asymmetrically placed toallow anterior or posterior fixation at the surgeon's discretion.Expansion slots can also be provided to specifically direct theexpansion of the fixation member so that the expansion can not onlyengage the bone engaging elements with the wall of the bone tunnel, butalso urge the graft material into closer association with the bonetunnel wall.

In still other embodiments, the graft receiving eyelet can be providedon a separate tip that includes a proximal expansion plug that canforceably mate with a distal plug receiving opening on the fixationmember. In this embodiment, proximal and distal expansion slots can beprovided, and in some cases, the proximal and distal expansion slots canencourage expansion in different directions. For example, one or moredistal slots can be employed to encourage expansion in a direction thatwill drive the opposed bone engaging elements apart so as to fix thefixation member to bone, while the one or more proximal slots canencourage expansion in a direction that will urge the graft materialinto closer contact with the bone tunnel walls. In this embodiment, itmay be desirable to size the plugs and plug receiving openings to allowthe proximal plug to enter the distal plug receiving opening first uponcompressing the system to forceably engage the plugs so that the graftmaterial does not bunch up upon fixation. This specific embodimentprovides still more proximal fixation which can be provided near theedge of a bone tunnel as desired.

Insertion and activation elements can also be provided. In any of thepreviously mentioned embodiments, a pull rod can extend through theexpansion plug and engage the distal-most element of the system while acannulated push tube can slide over the pull rod to engage the expansionplug. Relative movement between the pull rod and the push tube can thenforceably engage the elements.

In a method of the invention, a bone tunnel can first be formed, then afixation system as described above can be loaded with graft materialthrough the eyelet, and the fixation system and graft material can beinserted into the bone tunnel. Insertion into the bone tunnel can stopwhen the proximal end of the fixation member is substantially even withor slightly inside the edge of the bone tunnel. The fixation system canthen be actuated to fix the fixation member and the graft proximate tothe edge of the bone tunnel in the desired anatomically correctposition.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings.

FIG. 1 is a side view of a graft fixation system of the invention loadedwith graft material and mounted on an insertion member;

FIGS. 2, 2A and 2B are perspective, end and cross-sectional views of anexpanding fixation member of the graft fixation system of FIG. 1;

FIG. 3 is an exploded view of the graft fixation system of FIG. 1including an expanding fixation member, an expansion plug and a pullrod;

FIG. 4 is a side view of the graft fixation system of FIG. 1 withoutgraft material;

FIG. 5 is a side view of a graft fixation system of the invention havinga separate distal tip;

FIG. 6 is a plan view of graft fixation system of FIG. 5; and

FIG. 7 is a schematic view of an actuation device suitable for use withembodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a device, system, and method useful forfixing soft tissue graft material within a bone tunnel to replacedamaged ligamentary material and restore function to the portion of apatient's body in which the damaged ligamentary material was located.FIG. 1 provides an illustration of one such system of the inventionhaving a fixation member 20, an expansion plug 21 positioned at aproximal end 110 of the fixation member, and a graft material holdingelement in the form of an eyelet 24 located proximate to a distal end112 of the fixation member. Graft material 200 can be passed througheyelet 24 so that two ends 201 of the graft trail fixation member 20proximally. An insertion element 114 mates with fixation member 20 andexpansion plug 21 and extends proximally. In use, a surgeon insertsfixation member 20 along with graft material 200 into a prepared bonetunnel using insertion element 114 until the graft and fixation memberare in the desired position for graft fixation within the tunnel.Insertion element 114 can then be actuated or manipulated by the surgeonto force expansion plug 21 distally into fixation member 20 to cause thefixation member to expand and thereby fix the graft material to theinterior of the bone tunnel. Further details of this and otherembodiments of the invention are provided by reference to further FIGS.below.

As can be seen in FIGS. 2, 2A and 2B (which illustrate a side view, aproximal end view, and a lengthwise cross-section, respectively, offixation member 20), fixation member 20 includes cut out passages orgrooves 23 extending proximally along the fixation member from each ofthe two opposed sides of eyelet 24. In general, fixation member 20 willbe sized to fit closely into a bone tunnel of predetermined size.Typical grafts used to replace ligamentary material are compressible,and grooves 23 will be sized so that the graft material will be snuglypressed between the walls of the bone tunnel and grooves 23 uponinsertion of the fixation system into the tunnel.

Fixation member 20 also includes a proximal expansion plug receivingopening 22 which extends distally within the body of the fixationmember. Opening 22 is threaded in the illustrated embodiment in tworegions. A first threaded region 120, close to proximal end 110 offixation member 20, is threaded so as to engage expansion plug 21 whenthe plug is forced into the fixation member and lock the plug in place.A second threaded region 122, distal to region 120, is threaded toengage a pull rod 1002 (further described with respect to FIG. 3 below)that may be provided as part of insertion element 114.

On its external surfaces, fixation member 20 has a rounded or bulletshaped distal end to aid the surgeon in directing the fixation memberinto a bone tunnel. In addition, about its outer circumference (andgenerally not within grooves 23), fixation member 20 includes a seriesof opposed bone engaging elements 11, 12. As illustrated, bone engagingelements 11, 12 are fins that are angled proximally so that while theycan slide into a bone tunnel relatively easily, it will be moredifficult to pull fixation member 20 from a bone tunnel after insertionas the fins will dig into the walls of the bone tunnel (especially afterexpansion of the fixation element). While bone engaging elements 11, 12in this illustrated embodiment are angled fins, a person of ordinaryskill in the art will recognize that other bone engaging elements knownin the art, including for example asymmetric wedges, nitinol arcs, ormechanical elements that spring into cancellous bone, may be used asbone engaging elements on fixation member 20 within the spirit of theinvention.

One or more expansion slots 124 are also provided (two such slots 124are illustrated in FIG. 2) on fixation member 20 beginning at theproximal end 110 of the fixation member and extending distally throughthreaded region 120, generally extending at least as far as expansionplug 21 will be inserted into the fixation member. Slots 124 preferablydo not extend through the entirety of threaded region 122 to which apull tool may be attached as such an extension of slots 124 might weakenthe engagement between the pull tool and the fixation member. A personof ordinary skill in the art will recognize that the number and positionof the one or more expansion slots 124 can be varied from the number(two) and positions illustrated in FIG. 2 within the spirit of theinvention to allow fixation member 20 to expand upon insertion ofexpansion plug 21 so as to fix graft material to a bone tunnel wall. Inparticular, slot or slots 124 should be placed so as to result in anexpansion of fixation member 20 so that bone engaging elements 11 and 12move in opposed directions to force the bone engaging elements intoengagement contact with the bone tunnel wall to lock the fixation memberin place within the bone tunnel. It may also be desirable to place theslot or slots 120 so that fixation member 20 expands so as to forcegraft material pressed between grooves 23 and the bone tunnel wall intoeven more intimate contact therewith.

As can be seen in FIGS. 2 and 2A, bone engaging elements 11, 12 havedifferent lengths about the circumference of fixation member 20, withbone engaging elements 11 being larger and having a greater fixationregion than bone engaging elements 12. This difference in size resultsfrom an asymmetric placement of grooves 23. Each of the two grooves 23are specifically displaced in a direction toward bone engaging elements12 as the grooves extend generally proximally from graft eyelet 24. Thisasymmetry allows a surgeon to select a preferred direction for fixationof graft material within a bone tunnel. For example, for an ACLreplacement surgery requiring graft fixation in a bone tunnel formed ina patient's distal femur, the surgeon, for reasons of preference orowing to a specific fixation scheme, may wish to have a more anterior ormore posterior fixation of the graft material. Because graft materialwill be captured between grooves 23 and the walls of the bone tunnel,and because in the illustrated embodiment the grooves are asymmetricallyplaced, the surgeon may choose to insert the graft/fixation membersystem so that more of the graft material is captured against the bonetunnel in an anterior or posterior direction.

In addition to asymmetric sizing of bone engaging elements 11, 12,asymmetric placement of grooves 23 can result in asymmetric placement ofproximal opening 22. Proximal opening 22 must be placed so thatsufficient fixation member 20 material exists to provide strength forthreads in threaded region 120 and particularly in threaded region 122which may be used to securely attach fixation member 20 to a pull tool.Where grooves 23 are displaced toward bone engaging elements 12, thisrequirement can best be met by placing proximal opening 22 closer tobone engaging elements 11.

Turning now to FIG. 3 (showing an exploded view) and FIG. 4 (showing anassembled fixation assembly of the invention ready for graft placementand fixation), assembly and activation of a system of the invention willbe described. FIG. 3 illustrates a fixation member 20, an expansion plug21, and a pull rod 1002 in exploded view and ready for assembly. Asshown in FIG. 3, expansion plug 21 is larger in diameter than proximalplug receiving opening 22 of expansion member 20 so that, upon forceableinsertion of expansion plug 21 into opening 22, a forced expansion offixation member 20 is achieved as described above.

Expansion plug 21 includes external threads 126 which, although largerin diameter than threads in threaded region 120 of opening 22, arepreferably of the same pitch as the threads in threaded region 120 sothat when the expansion plug has been forced into the opening, threads126 will engage threaded region 120 to lock expansion plug in placewithin opening 22. While providing threads 126 and threaded region 120as elements for locking expansion plug 21 into opening 22 may beconvenient for reasons of manufacture, a person of ordinary skill in theart will recognize that a number of other locking elements could beprovided such as, for example, expanding locking elements provided onone of the plug or the opening that engage complimentary recessesprovided on the other of the plug or the opening, or a pin could beprovided on one of the plug or the opening to fit into an L-shapedrecess on the other of the plug or the opening so that followinginsertion and expansion, twisting of one component relative to the otherwould create a locking relationship that would prevent the plug frombacking out of the opening.

Expansion plug 21 may also include a tapered distal 128 configured toease entry of the expansion plug into opening 22. In addition, thedistal end of expansion plug 21 can include a removal tool engagingelement such as female hex 25. In the event that threaded expansion plug21 (which is cannulated as described below) should need to be removedfrom fixation member 20, a removal tool having a male hex head could beinserted through the plug cannula to engage female hex 25 to “unthread”a plug that would otherwise be locked into place.

In one exemplary embodiment intended for use in fixing graft material ina bone tunnel in a patient's distal femur for replacing a damaged ACL,fixation member 20 can have an overall length of approximately 0.995inches (with bone engaging elements 11, 12 extending along a length ofabout 0.390 inches) and a diameter from bone engaging elements 11 tobone engaging elements 12 of about 0.310 inches. Expansion plug 21 canhave a major diameter of approximately 0.180 inches and a minor diameterof about 0.160 inches while opening 22 can have a minor diameter ofabout 0.102 inches and a major diameter of about 0.113 inches. In thissame exemplary embodiment, expansion plug 21 can have a length ofapproximately 0.375 inches while expansion slots 124 can have a lengthof approximately 0.450 inches. A person of ordinary skill in the artwill recognize that these dimensions are provided only to give guidanceas to the construction of one embodiment of the invention, and thatparts described herein could have other dimensions, especially iftailored to different end uses. The component elements of the inventioncan be made from a variety of polymers and bio-absorbable polymers knownto be useful for implantable medical devices. In one embodiment, eachcomponent is formed from Delrin.

Also illustrated in FIG. 3 is pull rod 1002 which is part of insertionelement 114 (FIG. 1). Pull rod 1002 is sized pass through cannulatedexpansion plug 21 and into opening 22 in fixation element 20 wheredistal threads 1001 are configured to threadedly engage at leastthreaded portion 122 (FIG. 2B) within opening 22 so as to be releasablyengaged to fixation member 20. As further shown in FIG. 4, assembly ofthe fixation system to insertion element 114 involves sliding expansionplug 21 distally along pull rod 1002 until distal taper region 128 onthe plug engages opening 22 on fixation element 20, and sliding pushtube 1003 over pull rod 1002 so that a distal end 1005 of the push tubeabuts a proximal end of expansion plug 21. In order to provide bettersurface contact between push tube 1003 and expansion plug 21, a taperedor flared element 1004 may be provided adjacent the distal end of thepush tube. So assembled, the fixation system of the invention may beactuated by providing relative movement between pull rod 1002 and pushtube 1003 to force expansion plug 21 into opening 22 in fixation element20 to thereby lock the fixation element into a bone tunnel and fix graftmaterial to the tunnel wall.

In use in ACL replacement surgery, a surgeon would loop graft material200 through eyelet 24 to result in the configuration illustrated in FIG.1. The surgeon would next insert fixation element 20 (with attachedgraft material 200) into a prepared bone tunnel in the distal end of apatient's femur. Fixation element 20 is preferably inserted into thebone tunnel to such a depth that proximal end face 110 of the fixationelement is substantially even with or slightly inside the edge of thebone tunnel. The system can then be actuated by holding pull rod 1002 toprevent distal movement of fixation element while pushing on push tube1003 to force expansion plug 21 into opening 22 of fixation element 20,thereby expanding fixation element to fix the graft within the tunnel.By fixing the graft material in this way, with the fixation elementfixing the graft material right to its proximal end 110 and placing theproximal end near the edge of the bone tunnel, the graft will be fixedat or near the edge of the bone tunnel and the “windshield wiper” effectwill be reduced or eliminated.

A further embodiment of the fixation system of the invention isillustrated in FIGS. 5 and 6. In this embodiment, a distal tip 54 havinggraft receiving eyelet 24 is not integral with fixation member 50.Rather, tip 51 includes a curved or bullet shaped distal end 112, eyelet24 near the distal end, and a proximal plug 310 that engages fixationmember 50. Like expansion plug 21, proximal plug 310 on tip 51 includesthreads that are larger in diameter than a distal threaded opening 350on fixation member 50, but which have the same thread pitch as thethreaded opening 350 so that, upon forceable insertion, proximal plug310 will cause fixation member 50 to expand near its distal end 130 andthe threads will lock the tip to the fixation member. Proximal plug 310can also include an internal threaded region 311 to allow the tip to befixed to pull rod 1002 so that fixation element 50 may be actuated inthe same manner as fixation member 20.

Like fixation member 20 of the previously described embodiment, fixationmember 50 has opposed bone engaging elements 11, 12 and asymmetricallyplaced graft placement grooves 23. Tip 51 can also define a portion ofgrooves 23 distally from fixation member 50 to eyelet 24. Fixationmember 50 also includes a proximal threaded opening 55 for receivingexpansion plug 52 in substantially the same way that fixation member 20receives expansion plug 21.

Fixation member 50 further includes two separate pairs of expansionslots with slots 360 provided proximally to allow expansion frominsertion of expansion plug 52 and expansion slots 370 provided distallyto allow expansion from insertion of proximal plug 310 of tip 51. As isapparent in the embodiment illustrated in FIG. 6, expansion slots 360,370 are provided in different orientations to provide differingexpansion of fixation member 50 from the insertion of the differingplugs 52, 311, respectively. Distal expansion slots 370 are oriented toallow maximum expansion in a direction to allow bone engaging elements11, 12 to expand to lock fixation member 50 to a bone tunnel. Proximalexpansion slots 360 are oriented to allow maximum expansion in thegeneral direction of grooves 23 so as to force graft material located inthe grooves into tighter engagement with the bone tunnel wall near theproximal portion of the fixation element where fixation is most desired.

As is further clear from the embodiment illustrated in FIG. 6, distalthreaded opening 350 can have a larger diameter that proximal threadedopening 55. Where proximal plug 310 on tip 51 and expansion plug 52 haveapproximately the same diameter, this will cause proximal expansion plug310 to enter distal threaded opening 350 before expansion plug 52 entersproximal threaded opening 55. This can be advantageous where, as here,the distal portion of fixation member 50 expands primarily to lock boneengaging elements 11, 12 into the bone tunnel wall. In this way,fixation member 50 can lock within the tunnel, proximal ends 201 ofgraft material 200 can be pulled taught by the surgeon, and actuationcan continue with expansion plug 52 expanding a proximal portion offixation member 50 to press the graft material against the bone tunnelwall for optimal fixation. The system of FIGS. 5 and 6 can be insertedand actuated in the same manner as the embodiment of FIGS. 1 to 4.

FIG. 7 illustrates a schematic of a delivery device or handle assembly500 suitable for coupling to pull rod 1002 and push tube 1003 to actuatethe illustrated embodiments of the present invention. Handle assembly500 comprises a body having a handle grip 502. A trigger 505, having aplurality of fingers 507, is pivotally connected to body 501. Body 501also comprises a bore 508 opening on the body's distal end, and acounterbore 509 opening on the body's proximal end. A shoulder 509A isformed at the intersection of bore 508 and counterbore 509.

Handle assembly 500 also comprises a hollow ram 515. Ram 515 is sized sothat it can slidably accommodate pull rod 1002 within its inner diameterand so that it can be coupled to a proximal end of push tube 1003. Ram515 comprises a narrower distal portion 520 terminating in a distal tip510, and a wider proximal portion 525 including a plurality of teeth530. A shoulder 535 is formed at the intersection of narrower distalportion 520 and wider proximal potion 525. A slot 540 extends throughthe side wall of narrower distal portion 520.

Ram 515 is mounted in body 510 so that (1) the ram's narrower distalportion 520 extends through, and protrudes from, the body's bore 508,(2) the ram's wider proximal portion 525 is disposed in the body'scounterbore 509, and (3) the trigger's fingers 507 engage the ram'steeth 530. As a result of this construction, moving trigger 505 willcause ram 515 to move relative to body 501. A spring 545 is positionedin body 501, between body shoulder 509A and ram shoulder 535, so as tobias ram 515 in a proximal direction. A stop pin 550 extends intocounterbore 509 So as to limit proximal movement of ram 515.

Handle assembly 500 also comprises a gate 555 which includes an opening560 therein. Opening 560 defines a bottom wall 565 thereof. Gate 555 isdisposed in an opening 570 formed in body 501. A spring 575 biases gate555 against a locking pin 580, which extends through an oversized hole585 formed in gate 555. Gate 555 is disposed in body 501 so that thegate's bottom wall 565 normally protrudes, via ram slot 540, into theinterior of ram 515; however, pressing gate 555 downward against thepower of spring 575 will permit the gate's bottom wall 565 to be removedfrom the interior of ram 515.

In use handle assembly 500 is loaded over a proximal end of shaft pullrod 1002, and moved proximally down the shaft until the gate's bottomwall 565 starts to engage the ribs 1008 (see FIG. 5) of pull rod 1002.As this occurs, inclined proximal surfaces of ribs 1008 will allow thehandle assembly 500 to be moved distally along pull rod 1002 to theextent desired. However, by providing inclined surfaces on only theproximal sides of ribs 1008, the geometry of the ribs can prevent handleassembly 500 from moving back proximally along the shaft, unless, gate555 is pressed downward against the power of spring 575 so as to movethe gate's bottom wall 565 out of engagement with ribs 1008. Handleassembly 500 is moved down pull rod 1002 until the ram's distal endsurface 510 engages, or substantially engages, the proximal end 1010 ofpush tube 1003. Thereafter, pulling of the handle assembly's trigger 505will cause ram 515 to move distally along pull rod 1008, whereby pushtube 1003 can drive expansion plug 21, 52 into fixation member 20, 50,respectively, so as to fix fixation member 20, 50, and thus graftmaterial 200 in a bone tunnel.

The use of handle assembly 500 in conjunction with pull rod 1002 isoften preferred, since it permits pull rod 1002 to be held in placewhile ram 515 is advanced down pull rod 1002. More particularly,inasmuch as handle assembly 500 is releasably secured to pull rod 1002via the engagement of handle gate 555 with pull rod ribs 1008, handleassembly 500 can stabilize pull rod 1002 even as the handle's ram 515 isadvancing down pull rod 1002. This has been found to be advantageous inmany circumstances. Further details regarding the configuration and useof handle assembly 500 may be found in co-pending application Ser. No.09/510,770, filed Feb. 23, 2000, which is hereby incorporated byreference.

One of ordinary skill in the art will appreciate further features andadvantages of the invention based on the above-described embodiments.Accordingly, the invention is not to be limited by what has beenparticularly shown and described, except as indicated by the appendedclaims. All publication and references cited herein are expresslyincorporated herein by reference in their entity.

1. A ligament graft fixation system for fixing ligament graft materialwithin a bone tunnel comprising: an expandable fixation member havingopposed bone engaging elements disposed about its periphery, thefixation member having a proximal end, a distal end and an expansionplug receiving opening defined in the proximal end, at least one plugretaining element provided in the expansion plug receiving opening; agraft receiving eyelet disposed proximate the distal end of theexpandable fixation element; and a graft location groove provided on theexpandable fixation member extending proximally from the graft receivingeyelet; and an expansion plug having a diameter greater than a diameterof the expansion plug receiving opening and having an engaging elementmatable with the plug retaining element wherein forceable insertion ofthe expansion plug into the expansion plug receiving opening causes anexpansion of the expandable fixation member driving the opposed boneengaging elements apart so as to fix the bone engaging elements in abone tunnel.
 2. The ligament graft fixation system of claim 1, whereinat least one expansion slot is formed in a side wall of the expandablefixation member, the expansion slot adapted to direct expansion of theexpandable fixation member in a direction so as to drive the opposedbone engaging elements apart.
 3. The ligament graft fixation system ofclaim 2, wherein at least two expansion slots are provided.
 4. Theligament graft fixation system of claim 3, wherein the at least twoexpansion slots are provided asymmetrically about the periphery of theexpandable fixation member.
 5. The ligament graft fixation system ofclaim 1, wherein the expandable fixation member includes two graftlocation grooves, each groove extending proximally from one side of thegraft receiving eyelet.
 6. The ligament graft fixation system of claim5, wherein the grooves are asymmetrically located to allow for anterioror posterior graft fixation.
 7. The ligament graft fixation system ofclaim 1, wherein the at least one plug retaining element is a femalethread formed about the expansion plug receiving opening.
 8. Theligament graft fixation system of claim 7, wherein the engaging elementis a male thread disposed about a periphery of the expansion plug, themale thread having a pitch approximately equal to a pitch on the femalethread formed about the expansion plug receiving opening so that uponforceable insertion of the expansion plug into the expansion plugreceiving opening the male and female threads engage to hold theexpansion plug within the expansion plug receiving opening.
 9. Theligament graft fixation system of claim 1, wherein the expansion plug iscannulated and a pull rod engaging element is disposed on a distal endof the expansion plug receiving opening, the ligament graft fixationsystem further comprising a pull rod extending through the cannulatedexpansion plug and the expansion plug receiving opening and engaging thepull rod engaging element.
 10. The ligament graft fixation system ofclaim 9, wherein a cannulated push tube extends over the pull rod andabuts a distal end of the expansion plug.
 11. The ligament graftfixation system of claim 10, further comprising an actuation elementengaged to the pull rod and the push tube, the actuation elementproviding relative movement between the pull rod and push tube toforceably insert the expansion plug into the expandable fixation member.12. The ligament graft fixation system of claim 1, wherein the graftreceiving eyelet is provided on a tip having a proximal expansion plugand the fixation member defines a distal plug receiving opening, theproximal expansion plug sized so that, upon forceable insertion of theproximal expansion plug into the distal plug receiving opening, a distalportion of the expanding fixation member expands for fixing to a bonetunnel.
 13. The ligament graft fixation system of claim 12, wherein theexpanding fixation element has at least one proximal expansion slotguiding expansion of a proximal portion of the expanding fixation memberupon forceable insertion of the expansion plug and at least one distalexpansion slot guiding expansion of a proximal portion of the expandingfixation member upon forceable insertion of the proximal expansion plug.14. The ligament graft fixation system of claim 13, wherein the at leastone proximal expansion slot guides expansion of a proximal portion ofthe expanding fixation member in a first direction and the at least onedistal expansion slot guides expansion of a distal portion of theexpanding fixation member in a second direction different from the firstdirection.
 15. The ligament graft fixation system of claim 14, whereinthe at least one distal expansion slot guides expansion of a distalportion of the expanding fixation member to drive the opposed boneengaging members apart to fix the expanding fixation member in a bonetunnel.
 16. The ligament graft fixation system of claim 15, wherein theat least one proximal expansion slot guides expansion of a proximalportion in a direction for pressing a graft material against a bonetunnel wall.
 17. The ligament graft fixation system of claim 14, whereinthe proximal expansion plug sized so that, upon forceable compression ofthe expansion plug, expanding fixation member, and proximal plug, theproximal expansion plug is admitted into the distal plug receivingopening before the expansion plug is admitted into the proximal plugreceiving opening.
 18. The ligament graft fixation system of claim 12,wherein the expansion plug and the expanding fixation member arecannulated and a pull rod engaging element is disposed on a proximal endof the proximal plug, the ligament graft fixation system furthercomprising a pull rod extending through the cannulated expansion plugand expanding fixation member and engaging the pull rod engagingelement.
 19. The ligament graft fixation system of claim 18, wherein acannulated push tube extends over the pull rod and abuts a distal end ofthe expansion plug.
 20. The ligament graft fixation system of claim 19,further comprising an actuation element engaged to the pull rod and thepush tube, the actuation element providing relative movement between thepull rod and push tube to forceably insert the proximal plug and theexpansion plug into the expandable fixation member.
 21. A method forfixing a ligament graft in a bone tunnel comprising the steps of:forming a bone tunnel, the bone tunnel having a proximal edge; providinga ligament graft fixation system comprising: an expandable fixationmember having opposed bone engaging elements about its periphery, thefixation member having a proximal end, a distal end and an expansionplug receiving opening defined in the proximal end, at least one plugretaining element provided in the expansion plug receiving opening; agraft receiving eyelet disposed proximate the distal end of theexpandable fixation element; and an expansion plug having a diametergreater than a diameter of the expansion plug receiving opening andhaving an engaging element matable with the plug retaining elementwherein forceable insertion of the expansion plug into the expansionplug receiving opening causes an expansion of the expandable fixationmember driving the opposed bone engaging elements apart so as to fix thebone engaging elements in a bone tunnel; looping a ligament graftthrough the eyelet; inserting the ligament graft fixation system distalend first and ligament graft into the bone tunnel until the proximal endof the expanding graft fixation member is even with or slightly insidethe edge of the bone tunnel.